Abstract: Objective To explore the effect of ultra-low-dose wide-detector CT scanning mode on the radiation dose and excellent and good rate of image by coronary CT angiography(CTA) and its diagnostic value for coronary stenosis. 
Methods A total of 85 patients with suspected coronary heart disease(CHD) were selected as the research subjects, all of whom underwent Toshiba′s 320-slice spiral CT examination. The conventional group was tested with 100 kV tube voltage, and the ultra-low-dose group was tested with 70 kV tube voltage. The mean heart rate during the examination and radiation dose［CT dose index-volume(CTDIvol), dose-length product(DLP), effective dose(ED)］, objective evaluation parameters of image［optimal signal-to-noise ratio(SNR), contrast-to-noise ratio(CNR)］, image quality score, the excellent and good rate of image were compared between two groups. Digital subtraction angiography(DSA) was used as the gold standard, the consistency of the degree of coronary artery stenosis in ultra-low dose examination with DSA was evaluated, and its diagnostic value for coronary artery stenosis degree≥50%(moderate and above) was analyzed. 
Results CTDIvol, DLP, and ED in the ultra-low-dose group were lower than those in the conventional group, while SNR and CNR were higher than those in the conventional group, with significant difference(P＜0.05). After two senior diagnostic imaging physicians assessed the image quality with a double-blind method, there was no statistically significant difference between two groups in the image quality score and the excellent and good rate of image(P＞0.05). The agreement of the two doctors on the image quality assessment was high(Kappa value=0.772). With DSA examination as the gold standard, the ultra-low-dose wide-detector CT scan mode was consistent with DSA in the diagnosis of coronary stenosis(Kappa value=0.943). With DSA as the gold standard, the AUC of ultra-low-dose wide-detector CT scan mode in the diagnosis of coronary stenosis ≥50%(moderate and above) was 0.939. The sensitivity, specificity, and accuracy were 88.89%, 98.87%, and 98.16%, respectively. 
Conclusion The ultra-low-dose wide-detector CT scan mode has the advantages of higher objective evaluation of images and less impact on the excellent and good rate of image quality. It is helpful to reduce the radiation dose of patients undergoing coronary CTA examination, guide clinical assessment of coronary stenosis degree, and implement personalized treatment plan. 

Key words: coronary disease, ultra-low-dose wide-detector CT scan mode, Radiation dose